1. Field of the Invention
This invention relates to the field of additives, and, more specifically, to compatibilizers for composites of poly(vinyl chloride) (PVC) and cellulosic materials used as building materials for decking, railing, window profiles, roofing shingles, fencing, siding, furniture, and the like.
2. Description of Related Art
Composites of PVC with wood and other cellulosic fibers combine the particular properties of PVC, such as high rigidity, weatherability, low flammability (PVC is a self-extinguishing material), moisture resistance, low brittleness, and low density, and those of wood or other natural fibers (low price, esthetic appeal), in such a way that a new material with desirable qualities is obtained (See C. Bloyaert, PVC, the Definitive Choice for Sustainable Natural Fiber Composites, THE 9TH INTERNATIONAL PVC CONFERENCE (Brighton, U.K., 2005), and H. Jiang et al., Development of PVC/Wood Composites: A Literature Review, 10 J. VINYL ADDIT. TECHNOL. 59 (2004), and references cited therein.) Applications for wood-PVC include decking, railing, fencing, window profiles, doors, and flooring.
Wood-PVC composites have higher flexural modulus than PVC alone (see Bloyaert and Jiang et al., supra). Flexural strength, however, is lower than that for PVC (see Jiang et al., supra, and F. M. Meneloglu et al., 6 J. VINYL ADDIT. TECHNOL. 153 (2000)).
Improvement of mechanical properties is always desirable for composite materials, and it will lead to more durable materials that will also require less maintenance. The properties can be improved by the use of a compatibilizer. Possible approaches to improving mechanical properties by increasing adhesion between wood or cellulose and PVC include sizing (of wood or cellulose) and compatibilization. “Sizing” is the treatment of the fibers prior to their incorporation into the compound; “compatibilization” refers to an additive (compatibilizer) blended into the compound in order to enhance the mechanical properties of the final product. Wood sizing agents for wood-PVC that have been described include: silanes, silane/peroxide blends, polyisocyanates, mercaptans, maleic anhydride and phthalic anhydride with peroxides, maleated polypropylene/benzoyl peroxide, metallic complexes, such as chromated copper arsenate or copper ethanolamine, grafting acrylonitrile on wood flour (see Jiang et al., supra). Other materials reported as coupling agents include: chitin and chitosan (see B. L. SHAH ET AL., NOVEL COUPLING AGENTS FOR PVC/WOOD-FLOUR COMPOSITES, ANTEC 2005, USA), acrylic acid-functionalized polyethylene (PE) and maleic anhydride-functionalized PE (see Q. Li and L. M. Matuana, Surface of Cellulosic Materials Modified with Functionalized Polyethylene Coupling Agents, 88 J. APPL. POLYM. SCI. 278-86 (2003)), phthalic anhydride, maleic anhydride, and linoleic acid (Jiang et al., supra).
There are numerous publications on the use of alkoxy derivatives of silica (organo silanes) as sizing/coupling agents in plastics composites. The silanes, such as 3-aminopropyl triethoxysilane, and aluminates are typical materials of that sort (JP 08295774-1996; 32(1) WOOD AND FIBER SCIENCE 88-104 (January 2000); B. V. Kokta et al., Composites of Polyvinyl Chloride-wood Fibers III. Effect of Silane as Coupling Agent, 12(3) J. VINYL TECH. 146-53 (September 1990); Jiang et al., supra; L. M. Matuana, Influence of Interfacial Interactions on the Properties of PVC/Cellulocis Fiber Composites, 19(4) POLYMER COMPOSITES 446-55 (August 1998). Alkoxy derivatives of titanium (organo titanates) are also known as compatibilizers in the similar composite systems. Examples include titanium di(dioctylpyrophosphate)oxyacetate (11 INTERN. J. POLYMERIC MATER. 9-38 (1985). Alkoxy derivatives of zirconium (organo zirconates), such as cyclo[dineopentyl(diallyl)]pyrophosphato dineopentyl(diallyl)zirconate (also known as KZ TPP), as well as compounds of Ti, Si, and Al, are mentioned in literature as compatibilizers in a plastic fiber reinforced cementitious materials (WO 2004/028994) and in PVC filled with rubber dust (22 PLASTICS, RUBBER AND COMPOSITES PROCESSING AND APPLICATIONS 79-89 (1994)).
U.S. Pat. No. 5,514,734 discloses a process of forming a composite material comprising a polymer matrix comprising a polymeric material and dispersed particles selected from the group consisting of platelet or fibrillar particles having average thicknesses of less than 50 A and a maximum thickness of less than about 100 A and fibrils having an average diameter equal to or less than about 200 A and a maximum diameter of about 200 A and having an organo metallic species covalently bonded to said particles of organo metallic, and the organo metallic species having a moiety which is compatible with a polymer species in the polymer matrix, or said organo metallic species having a moiety which is covalently bonded to a polymer species in the polymer matrix or a combination thereof, said dispersed particles being present in an amount less than about 60% by weight of the composite material and to the composite material formed by such process.
U.S. Pat. No. 5,599,530 discloses an organic pigment particle having chemically bonded to its surface an organometallic zirconium compound, cosmetic compositions containing the pigment particles, and a method for reducing the staining potential of organic pigments.
U.S. Pat. No. 5,707,571 discloses a fiber reinforced, thermoplastic foam produced by dispersing fibers of controlled dimensions and blowing agent in molten thermoplastic and extruding the mixture with high back pressures. As the blowing agent expands, the fibers become randomly oriented and a fine cellular structure is formed in the plastic which freezes the fibers in a random spatial orientation.
U.S. Pat. No. 6,911,077 discloses a fiber reinforced cementitious material and the fiber used therein. The fiber reinforced cementitious material includes a conventional cementitious material and less than five pounds per cubic yard of the cementitious material of fibers dispersed therein. The fibers are made of a mixture of a thermoplastic polymer and an organometal compound wherein the metal of the compound is selected from the group consisting of Ti, Si, Zr, Al, and combinations thereof, with the organometal compound comprising less than 10% by weight of said fibers.
The disclosures of the foregoing are incorporated herein by reference in their entirety.